Ah, the age-old question and I'm wondering what the latest thinking is. I have a Dell Dim 2400 system. We generally put it on about 9:00 AM and leave it on. We use it about 3-6 hours sporadically during the day. At other times, it just sleeps and the screen is dark. At about midnight, I shut off the system. This means it might sit idle for maybe 3-6 consecutively. So my question: if I expect quite a few hours of non-use during the day, should I shut it off. (In fact, should I shut it off at night)? Mel